python - zip()、*号、namedtuple

在python里，*号代表拆分，把list/tuple里的元素拆出来，如：

tu = (1, 2, 3)
print(tu) # (1, 2, 3) tuple
print(*tu) # 1  2  3  各个元素
li = [(1,2,3), (4,5,6), (7,8,9)] 
print(li) #[ (1,2,3), (4,5,6), (7,8,9) ] 包含tuple的list
print(*li) # (1,2,3)  (4,5,6) (7,8,9) 各个tuple

list(zip(*li))

[(1, 4, 7), (2, 5, 8), (3, 6, 9)]

list(zip(*zip(*li)))

[(1,2,3), (4,5,6), (7,8,9)]

namedtuple是python collection里的一个类，有些类似于struct，一种简单的可以给元素命名的结构体，用法如下：

Friend = namedtuple("Friend",['name','age','email'])
F1 = Friend('giga', 38, 'gaga@qq.com')
print(F1)
print(F1.name, F1[0])
print(F1.age, F1[1])
print(F1.email, F1[2])

Friend(name='giga', age=38, email='gaga@qq.com')
giga giga
38 38
gaga@qq.com gaga@qq.com

同样，对待namedtuple Transitions，也可以这样：

Transition = namedtuple('Transition',('state', 'action', 'next_state', 'reward'))
T1 = Transition('A1', 'B1', 'C1', 'D1')
T2 = Transition('A2', 'B2', 'C2', 'D2')
T3 = Transition('A3', 'B3', 'C3', 'D3')
transitions = (T1, T2, T3)
batch = Transition(*zip(*transitions))
batch

Transition(state=('A1', 'A2', 'A3'), action=('B1', 'B2', 'B3'), next_state=('C1', 'C2', 'C3'), reward=('D1', 'D2', 'D3'))